Imagine the following model, where a User has a many to many
relationship with Message. A user can have many messages and messages
can be read by many users.
User <<----------->> Message
I can model this in EOModeler as a flattened relationship, and as
expected this will create the many-to-many indirection table
UserMessage for me.
User <------>> UserMessage <<----> Message
In the User entity it creates a relationship property messages() that
allows me to bypass the indirection table (and users() in Messages).
Now for the questions:
1 ==
In the "deprecated" EOModeler User Guide it states:
" Primary key propagation is also commonly used to generate primary
keys for join tables in many-to-many relationships."
If the join table has a compound primary key (consisting of the two
foreign keys to User and Message), how does this apply?
2 ==
Does anybody know how does WebObjects manage flattened relationships
internally?
Basically I want to know if (besides having more readable code) I get
some performance improvements using this.
So which are there any performance differences in these two?
user.messages();
or
user.userMessages().valueForKey("message");
3 ==
Now imagine I need to know if a user has read a message. I would
simply add a boolean to the indirection table to store this.
Can I still use the flattened relationships WebObjects provides and
store this boolean in the indirection table?
Are there any caveats I should be aware of?
4 ==
Theoretically if a message has no relation to users, it should be
deleted.
Does Owns Destination work in this many-to-many scenario?
5 ==
Not directly related to this scenario but I still couldn't quite
figure out:
When doing a addObjectToBothSideOfRelationship how does EOF know which
relationship is the inverse relationship?
In Core Data this is explicitly set but not in EOF.
Sorry if this was a bit too long, but I'm trying to tie up loose ends
in my mental model of EOF.
Thank you for your time,
Paulo F. Andrade
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